Adaptive robust motion control of single-rod hydraulic actuators: theory and experiments
TL;DR: In this paper, a discontinuous projection-based adaptive robust controller (ARC) is proposed for the swing motion control of a single-rod hydraulic actuator with constant unknown inertia load, which takes into account not only the effect of parameter variations coming from the inertia load and various hydraulic parameters, but also the effects of hard to model nonlinearities such as uncompensated friction forces and external disturbances.
Abstract: High-performance robust motion control of single-rod hydraulic actuators with constant unknown inertia load is considered. The two chambers of a single-rod actuator have different areas, so the dynamic equations describing the pressure changes in them cannot be combined into a single load pressure equation. This complicates controller design since it not only increases the system dimension but also brings in the stability issue of the added internal dynamics. A discontinuous projection-based adaptive robust controller (ARC) is constructed. The controller takes into account not only the effect of parameter variations coming from the inertia load and various hydraulic parameters but also the effect of hard-to-model nonlinearities such as uncompensated friction forces and external disturbances. It guarantees a prescribed output tracking transient performance and final tracking accuracy in general while achieving asymptotic output tracking in the presence of parametric uncertainties. In addition, the zero error dynamics for tracking any nonzero constant velocity trajectory is shown to be globally uniformly stable. Experimental results are obtained for the swing motion control of a hydraulic arm and verify the high-performance nature of the proposed strategy. In comparison to a state-of-the-art industrial motion controller, the proposed algorithm achieves more than a magnitude reduction of tracking errors. Furthermore, during the constant velocity portion of the motion, it reduces the tracking errors almost down to the measurement resolution level.
Citations
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TL;DR: The proposed controller theoretically guarantees a prescribed tracking transient performance and final tracking accuracy, while achieving asymptotic tracking performance in the absence of time-varying uncertainties, which is very important for high-accuracy tracking control of hydraulic servo systems.
Abstract: In this paper, an output feedback nonlinear control is proposed for a hydraulic system with mismatched modeling uncertainties in which an extended state observer (ESO) and a nonlinear robust controller are synthesized via the backstepping method. The ESO is designed to estimate not only the unmeasured system states but also the modeling uncertainties. The nonlinear robust controller is designed to stabilize the closed-loop system. The proposed controller accounts for not only the nonlinearities (e.g., nonlinear flow features of servovalve), but also the modeling uncertainties (e.g., parameter derivations and unmodeled dynamics). Furthermore, the controller theoretically guarantees a prescribed tracking transient performance and final tracking accuracy, while achieving asymptotic tracking performance in the absence of time-varying uncertainties, which is very important for high-accuracy tracking control of hydraulic servo systems. Extensive comparative experimental results are obtained to verify the high-performance nature of the proposed control strategy.
586 citations
TL;DR: In this article, a robust integral of the sign of the error controller and an adaptive controller are synthesized via backstepping method for motion control of a hydraulic rotary actuator.
Abstract: Structured and unstructured uncertainties are the main obstacles in the development of advanced controllers for high-accuracy tracking control of hydraulic servo systems. For the structured uncertainties, nonlinear adaptive control can be employed to achieve asymptotic tracking performance. But modeling errors, such as nonlinear frictions, always exist in physical hydraulic systems and degrade the tracking accuracy. In this paper, a robust integral of the sign of the error controller and an adaptive controller are synthesized via backstepping method for motion control of a hydraulic rotary actuator. In addition, an experimental internal leakage model of the actuator is built for precise model compensation. The proposed controller accounts for not only the structured uncertainties (i.e., parametric uncertainties), but also the unstructured uncertainties (i.e., nonlinear frictions). Furthermore, the controller theoretically guarantees asymptotic tracking performance in the presence of various uncertainties, which is very important for high-accuracy tracking control of hydraulic servo systems. Extensive comparative experimental results are obtained to verify the high-accuracy tracking performance of the proposed control strategy.
443 citations
TL;DR: In this paper, a practical method named adaptive robust control with extended state observer (ESO) is synthesized for high-accuracy motion control of a dc motor via a feedforward cancellation technique and theoretically guarantees a prescribed tracking performance in the presence of various uncertainties.
Abstract: Structured and unstructured uncertainties always exist in physical servo systems and degrade their tracking accuracy. In this paper, a practical method named adaptive robust control with extended state observer (ESO) is synthesized for high-accuracy motion control of a dc motor. The proposed controller accounts for not only the structured uncertainties (i.e., parametric uncertainties) but also the unstructured uncertainties (i.e., nonlinear friction, external disturbances, and/or unmodeled dynamics). Adaptive control for the structured uncertainty and ESO for the unstructured uncertainty are designed for compensating them respectively and integrated together via a feedforward cancellation technique. The global robustness of the controller is guaranteed by a feedback robust law. Furthermore, the controller theoretically guarantees a prescribed tracking performance in the presence of various uncertainties, which is very important for high-accuracy control of motion systems. Extensive comparative experimental results are obtained to verify the high-performance nature of the proposed control strategy.
375 citations
TL;DR: In response to uncertainties in systems and the possible actuator saturation, a saturated adaptive robust control (ARC) strategy is proposed, where an antiwindup block is added to adjust the control strategy in a manner conducive to stability and performance preservation in the presence of saturation.
Abstract: This paper investigates the problem of vibration control in vehicle active suspension systems, whose aim is to stabilize the attitude of the vehicle and improve ride comfort. In response to uncertainties in systems and the possible actuator saturation, a saturated adaptive robust control (ARC) strategy is proposed. Specifically, an antiwindup block is added to adjust the control strategy in a manner conducive to stability and performance preservation in the presence of saturation. Furthermore, the proposed saturated ARC approach is applied to the half-car active suspension systems, where nonlinear springs and piecewise linear dampers are adopted. Finally, the typical bump road inputs are considered as the road disturbances in order to illustrate the effectiveness of the proposed control law.
355 citations
TL;DR: In this article, an adaptive sliding control method is presented for an electro-hydraulic system with nonlinear unknown parameters, which enter the system equations in a nonlinear way. But in practical hydraulic systems, the original control volumes are unknown or change; as a result some unknown parameters appear nonlinearly.
334 citations
References
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Book•
01 Jan 1995
TL;DR: In this paper, the focus is on adaptive nonlinear control results introduced with the new recursive design methodology -adaptive backstepping, and basic tools for nonadaptive BackStepping design with state and output feedbacks.
Abstract: From the Publisher:
Using a pedagogical style along with detailed proofs and illustrative examples, this book opens a view to the largely unexplored area of nonlinear systems with uncertainties. The focus is on adaptive nonlinear control results introduced with the new recursive design methodology--adaptive backstepping. Describes basic tools for nonadaptive backstepping design with state and output feedbacks.
6,923 citations
Book•
01 Jan 1989TL;DR: In this paper, the deterministic theory of adaptive control (AC) is presented in an introduction for graduate students and practicing engineers, with a focus on basic AC approaches, notation and fundamental theorems, identification problem, model-reference AC, parameter convergence using averaging techniques, and robustness.
Abstract: The deterministic theory of adaptive control (AC) is presented in an introduction for graduate students and practicing engineers. Chapters are devoted to basic AC approaches, notation and fundamental theorems, the identification problem, model-reference AC, parameter convergence using averaging techniques, and AC robustness. Consideration is given to the use of prior information, the global stability of indirect AC schemes, multivariable AC, linearizing AC for a class of nonlinear systems, AC of linearizable minimum-phase systems, and MIMO systems decouplable by static state feedback.
2,914 citations
"Adaptive robust motion control of s..." refers background in this paper
...Let denote the estimate of and the estimation error (i.e., ). Viewing (8), a simple discontinuous projection can be defined [ 21 ], [22] as...
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Book•
01 Jan 1991
TL;DR: In this article, the authors present an overview of the properties of hydraulic fluids and hydraulic power in control systems, including pressure and flow control Valves, and hydraulic pumps and motors.
Abstract: Hydraulic Fluids. Fluid Flow Fundamentals. Hydraulic Pumps and Motors. Hydraulic Control Valves. Hydraulic Power Elements. Electrohydraulic Servovalves. Electrohydraulic Servomechanisms. Hydromechanical Servomechanisms. Nonlinearities in Control Systems. Pressure and Flow Control Valves. Hydraulic Power Supplies. Index.
2,044 citations
TL;DR: This paper considers the adaptive robust control of a class SISO nonlinear systems in a semi-strict feedback form and develops a systematic way to combine the backstepping adaptive control with deterministic robust control.
671 citations
"Adaptive robust motion control of s..." refers background or methods in this paper
...... condition 1 of (17) represents the fact that is synthesized to dominate the model uncertainties coming from both parametric uncertainties and uncertain nonlinearities with a control accuracy measured by the design parameter , and condition 2 is to make sure that is dissipating in nature so that it does not interfere with the functionality of the adaptive control part . How to choose to satisfy constraints like (17) can be found in [ 14 ] and ......
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...reduce transient tracking error, the reference trajectory initialization can be used as in [ 14 ], [15], and [20]....
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...It is shown in [ 14 ] and [20] that such a trajectory initialization is independent from the choice of controller parameters and and can be performed offline once the initial state of the system is determined....
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...In fact, when the parameter adaptation law (10) is switched off, the proposed ARC law becomes a deterministic robust control law and results 1) of the Theorem remain valid [13], [ 14 ]....
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...... contain control input ; this difficulty can be overcome by employing backstepping ARC design as done in the following; 2) the nonlinear static flow mappings and are functions of also and are nonsmoothsince they depend on the sign of ; this prohibits the direct application of the general results in [15] to obtain an ARC controller, which need the differentiability of all terms; and 3) as will become clear later, the “relative degree” [ 14 ] ......
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TL;DR: Simulation and experimental results show that the active system is better than a passive system in terms of improving the ride quality of the vehicle and both of the adaptive schemes improve performance, with the modified scheme giving the greater improvement in performance.
Abstract: In this paper, a previously developed nonlinear "sliding" control law is applied to an electro-hydraulic suspension system. The controller relies on an accurate model of the suspension system. To reduce the error in the model, a standard parameter adaptation scheme, based on Lyapunov analysis, is introduced. A modified adaptation scheme, which enables the identification of parameters whose values change with regions of the state space, is then presented. These parameters are not restricted to being slowly time-varying as in the standard adaptation scheme; however, they are restricted to being constant or slowly time varying within regions of the state space. The adaptation algorithms are coupled with the control algorithm and the resulting system performance is analyzed experimentally. The performance is determined by the ability of the actuator output to track a specified force. The performance of the active system, with and without the adaptation, is analyzed. Simulation and experimental results show that the active system is better than a passive system in terms of improving the ride quality of the vehicle. Furthermore, both of the adaptive schemes improve performance, with the modified scheme giving the greater improvement in performance. >
562 citations
"Adaptive robust motion control of s..." refers background or methods or result in this paper
...YDRAULIC systems have been used in industry in a wide number of applications by virtue of their small size-topower ratios and the ability to apply very large force and torque; examples like electrohydraulic positioning systems [1], [2], active suspension control [ 3 ], and industrial hydraulic machines [4]....
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...dynamic equations relating the pressure changes in the two chambers to the servovalve opening cannot be combined into a single equation that relates the load pressure to the valve opening as in [ 3 ], [5], [12], and [17]....
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...In [ 3 ], Alleyne and Hedrick applied the nonlinear adaptive control to the force control of an active suspension driven by a double-rod cylinder, in which only parametric uncertainties of the cylinder are considered....
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...First, unlike other experiments [ 3 ], [19] where high bandwidth servovalves with spool position feedback is used, our system is designed to mimic typical industrial use of electrohydraulic systems....
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